16 



IRRIGATION PRACTICE 



of the periods, the grain crops and the peas were prac- 

 tically ripened. No noticeable injury from wilting was 

 observed. Some of the results are presented in the fol- 

 lowing table: 



The hygroscopic coefficient of the soil was about 5 

 per cent, which would make the wilting coefficient about 

 7J/2 per cent. In only one case, that of wheat, did the 

 soil moisture go below this point in the first foot; and, in 

 every case, the percentage of soil moisture to a depth of 

 6 to 8 feet, through all of which root-action was felt, was 

 above the calculated wilting coefficient. 



17. Lento-capillary point. The water in the soil- 

 moisture film corresponding to the wilting coefficient is 

 held so firmly that plants can absorb it with difficulty. 

 As more water is added to the soil, to thicken the film, 

 the more loosely is the water held, and consequently the 

 more easily can plants secure it. As this thickening 

 goes on, a point is reached above which the film water is 

 held so loosely that it moves freely from soil particle to 

 soil particle under the influence of the forces in the soil. 

 This has been called the lento-capillary point. The water 

 above this point is readily available to plants, and con- 

 stitutes the main supply of water for plants under irri- 

 gated conditions. 



